If there’s one area in which energy recovery seems like a natural fit, it’s in recapturing and reusing heat, because plastics facilities generate a lot of it.
For auxiliary equipment like ovens and dryers, producing heat is what they were created to do.
Once the heat has done its primary job, such as curing composite parts in an oven, it is often allowed to dissipate, even though it could be used for another purpose.
Leister Technologies has developed a hot-air recycling system that does exactly that. Conceptually, it’s simple.
A blower pushes air through a heater and into a dryer or an oven; the heated air comes out of the oven and is redirected back to the blower to begin the cycle again – only this time it starts with very hot air that was recirculated rather than dissipated.
The tricky part, according to Jason Sanders, product specialist, was creating components that could handle the heat.
“To recycle the hot air from a process, both the blower and the air heater need to be able to withstand the high temperatures at the air-inlet side,” he said.
Leister’s solution consists of one of its double-flange air heaters — either the LE 5000 DF-R or LE 10000 DF-R — and its RBR blower; those heat-resistant components are able to endure temperatures up to 600˚F.
For a long time, the vulnerability of an electrical cable held the company back, but it found a heat-resistant cable and insulated it to provide even more protection, enabling the system to function up to the 600-degree level.
The upper limit could be a lot higher but that’s as much heat as the cable can withstand, even with the insulation.
The heater and blower components can withstand temperatures as high as 1,112 degrees, so even greater energy recovery would be possible if a more heat-resistant cable could be used.
The pay-off of hot-air recirculation can be substantial. Without it, a system with an airflow of 4,000 litres per minute, operating 24 hours a day, 220 days per year, would consume about 202,315 kilowatt-hours (kWh) of energy.
When equipped with one of Leister’s double-flange air heaters and the RBR blower, energy consumption is almost cut in half, requiring only 106,482kWh.